When comparing C++ vs Haxe, the Slant community recommends Haxe for most people. In the question“What is the best programming language to learn first?”Haxe is ranked 25th while C++ is ranked 27th. The most important reason people chose Haxe is:

Haxe allows you to develop for Web, iOS, Android, Blackberry, Windows, OSX, Linux and others, all at once, without the need to switch languages and maintain separate code bases.
This is possible because Haxe can compile to JavaScript, ActionScript, Flash AVM bytecode, C++, Neko, PHP, C# (.NET) and Java.
Support for even more platforms and languages is under development.

Pros

Pro

Huge language supports most everything

C++ is a large language with an even larger community and following. It has libraries for every kind of task that is possible to do with C++

Pro

Powerful memory management

Allows puting large arrays on the "heap" to avoid "stack overflow".

Pro

Teaches fundamental OOP

Teaches you to leverage object oriented programming.

Pro

Excellent compiler optimization

Both open source compilers (such as Clang and GCC), and proprietary ones (like Intel's and Microsoft's) are very good at analyzing program flow and program optimization. This is mostly due to the widespread usage of C/C++ applications running everything from mobile/desktop/server Operating Systems, to search engines and webserver software, and the demand for performance.

Pro

Teaches problem solving

The great STL is the most powerful Data Structure and Algorithms Library. It would benefit you very much in problem solving, your main main way to love programming. The code is much compact compared to Java and C#. No unnecessary classes are in your way; yet when you need classes they are available unlike C. The code runs very fast.

Pro

Best way to understand algorithms

Pro

C code can be used in C++ code

Most C code will work as C++

Pro

STD is often updated

The functionalities keep growing throughout the years. C++11 gave us a soft type of garbage collecting with the smart pointers.

Pro

Compiles to multiple platforms and languages

Haxe allows you to develop for Web, iOS, Android, Blackberry, Windows, OSX, Linux and others, all at once, without the need to switch languages and maintain separate code bases.

This is possible because Haxe can compile to JavaScript, ActionScript, Flash AVM bytecode, C++, Neko, PHP, C# (.NET) and Java.

Support for even more platforms and languages is under development.

Pro

Powerfully expressive but easy to learn

The language was designed to be very expressive with the smallest possible amount of syntactic sugar. There are actually fewer keywords than other languages with similar power.

Pro

Pick up errors at compile time

One big advantage over pure javascript, (or some other languages listed here) is that Haxe will pick up a whole range of errors when you compile, saving you the pain of having to try and debug them later. This includes everything from syntax errors ("Unexpected ;") to type errors ("Class user has no field username. Suggestion: username").

Pro

First class code completion

Code completion is built into the compiler and available to the IDE allowing for much smarter code completion that can actually parse and understand the syntax tree.

Pro

Code reuse server side and client side

You can use the same classes on the server as you do on the client where applicable. This saves a lot of time.

Pro

Syntactic macros

Syntactic macros allow you to extend compiler features at the syntax tree step. Macros come into play after code is parsed into the abstract syntax tree, and macros allow you to transform it before the rest of the compilation completes.

This provides for immense power, while at the same time scoping the extensibility at a level that is powerful, but well constrained.

Pro

Extremely fast compilation.

Haxe can easily compile over 100,000 lines of code to JS in seconds on a mid-spec computer

Pro

Ability to use existing JS libraries

Haxe has the ability to use "externs". These are haxe files which describe the usage of existing JS libraries. Get code completion and compile-time-checking for everything from jQuery to Node.js.

Even without externs, native JS code can still be used through untyped code.

Pro

Similar to JavaScript and ActionScript 3

The language is very easy to learn for those with background in JavaScript or ActionScript 3.

Pro

Large library support. From servers to games.

Haxelib (common library repo) and other sources contain large codebases for anything from cryptography to communications. A lot of these are fully cross platform and work with the JavaScript target.

The JavaScript target can be used for everything from node.js server applications (with code completion) to games using either the Flash-like OpenFL library or direct canvas or WebGL programming.

Pro

Small, readable output

The output that is generated can be trimmed using "dead code elimination" to only include those functions and libraries that are strictly necessary. All code is very readable with only minimal extras for specific functionality.

Small output is good for frontend development as file size is a major concern.

Pro

Established project.

Haxe has been around for more than 10 years (since 2005) and whilst not the most popular project, has had continuous growth.

Highly unlikely to disappear or for support to stop.

Pro

Powerful type inference with strong typing

After a type is inferred from its context, it cannot be changed to a new type, and type safety is done at compile time so it stays safe without the extra maintenance required for static typing.

Pro

Algebraic data types and pattern matching.

Pro

Friendly community

Friendly community

Pro

Offload execution to the server with remoting

Using a remoting proxy you can get type safe server to client communications, allowing for remote method execution on the server as if they were part of the client side code.

Pro

Package management like Java

Package tree is just directory tree, it's wonderful!

Pro

Available in NPM

Pro

Builtin conditional compilation support

Haxe supports conditional compilation, so depending on compiler flags Haxe will include or exlcude sections of your code. Making it easy to have debug and release builds.

Pro

Create without needing to be limited to a language, target, or commercial ecosystem

Pro

Type safety for exísting JS libraries

Haxe compiler will check types when using externs for existing libraries.

Pro

Can create complex applications without needing webpack, npm or other crutches, unless I want.

Haxe has the power and expression to not need the npm dependancy hell that is common in js and typescript, bit it's still simple.

Pro

Abstract enums allow constants with exhaustiveness check

You can define constants in an abstract enum and when used in a switch/case statement Haxe checks for exhaustiveness, making sure every constant is covered - with no runtime implication.

Pro

Pro

Ability to skip type checking when calling non Haxe code

You should use externs when calling non Haxe code, but if you just need to call one or two external JS functions, you can skip type checking by calling untyped code.

Cons

Con

Huge language gets in the way of learning

C++ is such an atrociously over-complicated language that its learning curve may get in the way of learning fundamentals. Learning C++ well is a ten-year project, and even experts are frequently surprised by the language.

Con

Module system is not great

C++ uses the #include mechanism provided by C. Which unfortunately is a poor way of accessing the API of a library. Some of the reasons why the module system is weak are:

Compile time scalability: The compiler must preprocess every header included in a file, and every header included in those headers. This process must be repeated for every translation unit in the program. As can be imagined, this doesn't scale very well. For each header added you are increasing the compilation time exponentially.

Fragile: modules included are treated as textual imports by the compiler. This causes all sorts of problems since they are subject to any macro definitions in the time of the inclusion. If any of these macro definitions collide with a name in the library it can break the library API .

Con

Undefined behavior

Subtle errors can render the entire program "undefined" by the complicated C++ standard. The standard imposes no requirements in such cases. Thus C++ compiler writers are free to ignore the existence of such cases and Bad Things are prone to happen instead. Even experts can't reliably avoid undefined cases in C++, so how can beginners be expected to do so?

Con

No two programmers can agree on which 10% subset of C++ to use

C++ is such a huge and complicated language, that programmers have to learn a disciplined subset of it to reliably get anything done. The problem is, no-one can agree on which subset to use and they can't understand each other.

Con

Retains nearly all bad habits of C

Con

Painfully slow compilation

Beginners need fast feedback

Con

Bugs easily corrupt the memory you need to find them

You can usually get a core dump, but often the call stack gets completely overwritten. Compilers are not even consistent in how they map the binary objects to code.

Con

Complicated types

Con

Standard library missing important features

Con

Arcane binding rules

Con

Tough to learn as the first language

Many of the concepts are hard to grasp if you have no prior programming experience.

Con

Duplicates C features in incompatible ways

Arrays, strings, pointers, etc. have both C and C++ versions. Sometimes the C++ versions are worse. This is more useless trivia beginners have to sort through.

Con

Incomprehensible operator overloading resoution

Con

Exceptions incompatible with C++ manual memory management

Con

No way to locate definitions

No modules, just files, and no way to tell where anything came from.

Con

No reflection

C++ objects are frustratingly opaque. This makes debugging especially difficult, something beginners have to do a lot.

Con

You need to code interfaces to work with existing JavaScript code

Some popular libs like JQuery have maintained externs, for any specific code or lib already in JS you have to write the externs to use it in your haxe application.

Con

Bad support in some popular IDEs

While it has great support in Visual Studio Code and Vim for example, it still lacks support in some IDEs such as IntelliJ.

Con

No Qt support

There is currently no support for Qt.

Con

Full programs only

You can create small utility functions with Haxe, but generally it is a lot more work than with other JS compilers. Haxe is best used when you have a larger project.

Con

It's not easy to convince people it's as good as it really is unless you can get them to really try it